The invention disclosed and claimed herein pertains generally to systems which include a platform suspended in an underwater environment to resist angular or other motion as equipment which is joined to the platform is controllably displaced in various degrees of motion. Even more particularly, the invention pertains to such systems wherein the platform interacts with a current present in the underwater environment in order to remain immobile as the equipment joined thereto is controllably displaced.
Certain equipments intended for operation in an underwater environment, such as an ocean body, must be selectively displaceable in one or more degrees of freedom or motion in order to accomplish desired tasks. For example, a hydrophone placed in an underwater environment to track or monitor a submarine may have to be rotatable in both a horizontal plane (azimuthal motion) and in a vertical plane (elevational motion) in order to follow a submarine as it moves through the environment. It will be readily apparent that if such equipments are not stabilized in some manner, controlled motion thereof will generate motion which is not controlled. For example, if the above hydrophone is suspended from a cable, the cable may be twisted as the hydrophone is turned through an azimuth. The twisting of the cable stores a potential energy which, upon release, will cause the hydrophone to be shifted from a desired position, if stability is not in some way provided thereto.
In a prior art system for resisting uncontrolled azimuthal motion of equipment suspended in an underwater environment, the equipment is mounted on a structure which includes an elevation trunnion and an azimuth gimbal. A servo motor is mounted on a stabilizing unit which has fins thrust outwardly into the environment. As the servo motor turns a shaft joined to the equipment, the equipment is rotated through an azimuth, while the fins resist azimuthal motion of the stabilizing unit in the water. However, such a prior art system generally requires a special winch for deployment and recovery so that its use is limited to specially equipped vessels, or else a suitable winch must be provided as part of the system. In addition, the system is deployed by suspending it from a single cable, which also includes power conductors for conveying electric power to the servo motor. As the servo motor rotates the shaft, there is sufficient azimuthal drift of the stabilizing unit that the cable is twisted enough to store a disruptive amount of potential energy. Also, slip rings are required to couple the power conductors of the cable to the servo motor as the cable is twisted. As a further disadvantage, such prior art system does not provide for controlled elevational displacement of equipment employed therewith, due to the use of a trunnion for mounting the equipment.
In a stabilizing system which improves over the above prior art, the need for comparatively expensive slip rings should be eliminated. Also, the azimuthal drift of a stabilizing platform included in the system should be eliminated or sufficiently reduced to prevent storage of potential energy in a cable from which the system is suspended. Such improved system should also provide stability for elevational or vertical displacements of equipment, as well as for azimuthal displacements thereof.